Honda Express Build Thread

General Discussion about large electric scooters and motorcycles and other things with no pedals.
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quasse   100 µW

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Honda Express Build Thread

Post by quasse » May 18 2014 11:00pm

A few years ago I bought a Honda NC50 Express moped hoping to restore it and use it to ride around town. Unfortunately it only ever ran terribly if at all, and upon disassembly it became clear that the previous owner had ruined the engine by running it through dirt and mud without an air filter. The cylinder was scored and many of the bearings were rusted.
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After wasting a lot of money and time trying to get the engine running I decided I would much rather convert to to electric instead. I wanted to do as economical of a build as possible using an outrunner, because I had only ever used hub motors before and their cost was prohibitive. Thus started my 50CC to outrunner conversion.

I decided on using a Turnigy SK3 6374. To determine the correct kV rating I did some quick calculations using the transmission ratios and the size of the wheels:
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As you can see, with an input of 48v and a 168kV motor, I calculated a ground speed of 31 mph. Of course, in the real world this would be slower due to efficiency losses, but this was in the ballpark of what I wanted. I purchased this motor: https://www.hobbyking.com/hobbyking/sto ... Motor.html

I took apart the transmission:
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And split the case and removed the piston and jug:
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You can see how bad the crankshaft was in the photo above.

I decided that I wanted to use the entire original crankcase, because the frame mounting bushings were cast into the top (you can see one in the photo above), so I was going to have to create some kind of replacement crankshaft to adapt the outrunner to the original clutch and transmission.

I originally thought I would cut the original crankshaft in half and drill a hole for the outrunner's shaft to fit into. With that in mind I cut everything except the clutch bearing faces off the crankshaft:
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Since I was going to mount the motor on the side of the crankcase opposite the clutch, I would have needed to weld a piece of round stock on to the remaining piece of the crankshaft to bridge the gap. I decided that it would be harder to weld something completely straight that it would be to machine a new one, so I ended up just taking careful measurements of the shaft and creating a new one from aluminum:
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Next up was creating a good place in the non-clutch side of the crankcase to mount a motor. That side originally held the flywheel and ignition system, and had a lot of geometry cast into it. I clamped it in the mill and machined everything flat:
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I cut out a sloppy little plate on the bandsaw and drilled a hole for the motor shaft, along with threaded holes for the motor mount:
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While I was at it I tapped out the bearing and replaced it with a sealed unit rated for sufficient RPM:
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Here you can see the new bearing with the custom crankshaft:
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The hole is for the outrunner shaft, I machined a groove into the outrunner shaft and put a set screw inside the new crankshaft to lock them together.

Here is where the piston would have used to be, as you can see it's just a straight aluminum shaft now:
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And here is where the clutch would sit (I later threaded the end of the shaft for the clutch lock nut):
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At this point I had pretty much figured out the entire drivetrain and needed to start on electronics. I did not want to use a sensorless controller so I did quite a bit of research into adding external hall effect sensors to outrunners. I found that I needed some way to mount them 17.14 degrees apart around the case of the motor. For this, I turned to 3D printing and whipped up a quick mount on the RepRap:
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I drilled some holes in a piece of aluminum stock and used that to mount the sensors in the motor side of the crankcase on the same plate I had made earlier:
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I'm ashamed of how bad my wiring job is haha, fixing that is the first thing on the todo list once I get things close to done. At this point I was able to reassemble the moped and get everything mounted up! Here's the entire rear end of the moped with the motor installed:
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This is where it is today, I'm pretty pleased with how it's turning out. I got around to bolting the rest of the frame on and installing a throttle today, here's the very first run of the motor:


As you can see, my controller is still sitting on the ground and my batteries are in a bike pannier. Fabbing up some kind of battery box is the last thing I need to do before it'll be ready for its first real ride! At this point I'm thinking I'll use the mounting points that were originally designed for the fuel tank (now obsolete of course) and create some kind of aluminum battery box that mounts to them over the rear wheel like you can see in the first picture.

I'm also somewhat unhappy with the adjustability of my hall sensor mounts and the wiring they required. I ordered an Equals Zero designs http://e0designs.com/products/hall-effect-sensor-board/ hall sensor board and adapter and I'll be switching to that when it arrives.

Hopefully this week I'll have time for some work on that, as well as getting some basic stuff like brakes working. I'll update the thread as things happen, but I'm pretty excited to be close to having a rideable moped.

John in CR   100 GW

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Re: Honda Express Build Thread

Post by John in CR » May 19 2014 11:53am

Excellent. A buddy has several Honda Expresses, and I gave him an 80/100 outrunner to do exactly what you've done.

I was thinking that the centrifugal clutch should allow the use of an RC ESC and not worry about the hall sensors.

quasse   100 µW

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Re: Honda Express Build Thread

Post by quasse » May 22 2014 12:42pm

I took it out for a few shakedown runs this week and it seems to be running pretty well. It pulls hard at low speed and runs up to about 25mph with 48v.

The problem is that there doesn't seem to be a timing setting that works everywhere. If I set it so that it can spin up to full speed without cutting out I get cogging at low speed and up to about 5000rpm. If I set it up to stop the low speed cogging and juddering, the controller cuts out at about 7000rpm and I need to close the throttle and reopen it to get it going.

I'm not sure what to do at the moment, I'm really hoping I don't need to go to a variable timing system like Burtie makes.

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gwhy!   1 MW

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Re: Honda Express Build Thread

Post by gwhy! » May 27 2014 10:53am

quasse wrote:I took it out for a few shakedown runs this week and it seems to be running pretty well. It pulls hard at low speed and runs up to about 25mph with 48v.

The problem is that there doesn't seem to be a timing setting that works everywhere. If I set it so that it can spin up to full speed without cutting out I get cogging at low speed and up to about 5000rpm. If I set it up to stop the low speed cogging and juddering, the controller cuts out at about 7000rpm and I need to close the throttle and reopen it to get it going.

I'm not sure what to do at the moment, I'm really hoping I don't need to go to a variable timing system like Burtie makes.
what controller are you using ?

quasse   100 µW

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Re: Honda Express Build Thread

Post by quasse » May 27 2014 1:39pm

gwhy! wrote: what controller are you using ?
The EM3EV 9 fet IRFB4110 Infineon, which I bought based on people's recommendations that it could likely handle high eRPMs. Luckily the problem doesn't seem to have been controller related but was because of my 3D printed hall sensor mount.

I got my new mount from e0designs this week and soldered some halls into it and the problem has gone away. I think my spacing must have been off slightly on my 3D printed one, it seems that these controllers are extremely sensitive to small errors in hall mounting when you have the motor running at high speed.

Now I just need to figure out a good battery mounting solution. I'm thinking of either TIG welding an aluminum enclosure or laser cutting something from wood.

stev151   1 µW

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Re: Honda Express Build Thread

Post by stev151 » May 27 2014 1:44pm

quasse wrote:
gwhy! wrote: what controller are you using ?
The EM3EV 9 fet IRFB4110 Infineon, which I bought based on people's recommendations that it could likely handle high eRPMs. Luckily the problem doesn't seem to have been controller related but was because of my 3D printed hall sensor mount.

I got my new mount from e0designs this week and soldered some halls into it and the problem has gone away. I think my spacing must have been off slightly on my 3D printed one, it seems that these controllers are extremely sensitive to small errors in hall mounting when you have the motor running at high speed.

Now I just need to figure out a good battery mounting solution. I'm thinking of either TIG welding an aluminum enclosure or laser cutting something from wood.
What battery arrangement are you going to be doing?

Are you mounting them on the back rack?

quasse   100 µW

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Re: Honda Express Build Thread

Post by quasse » May 27 2014 2:01pm

48v HK LiPo. I'm thinking 12s2p, so four of the large 6S packs.

I was thinking of doing a custom rear rack origninally (I sold the stock one with the fuel tank) using the mounting holes for the original, but I also noticed that there is a space between the front foot rests that could fit a battery box. It's where the cylinder head for the engine used to go and would be a good way to keep a low center of gravity.

quasse   100 µW

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Re: Honda Express Build Thread

Post by quasse » Jun 17 2014 8:31pm

I've made a decent amount of progress since last time, things are now assembled for the most part and it's very ridable. I even managed to get it road legal by having a friend register it for me in MN :roll:

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I laser cut a new battery box and mounted it in the rear rack, my wiring is still a bit of a mess though:

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You can see the new hall effect sensor mount I'm using now, it's much more reliable.

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It's a moped of many zipties right now:

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Here's a video of a run up and down my block, it sounds pretty nice and pulls hard up to about 25mph:

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Kent   1 kW

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Re: Honda Express Build Thread

Post by Kent » Jun 17 2014 10:59pm

Congrats on a very innovative build! It semes like the perfect town runabout!

Can you give us a ballpark on finished weight and tire size?
72 V, (2x36v, 11.5 ah in series) Cellman, HS3540, 18fet Lyen, Jamis Dirtjumper Hardtail. Its streetlegal w license plate, inspection sticker.

Only by setting an example of good road manners and public courtesy can we convince the general public to take the electric bike seriously as a transportation option. Obey traffic laws!

My build: http://endless-sphere.com/forums/viewto ... =6&t=45706
Going legal: http://endless-sphere.com/forums/viewto ... =3&t=49390

GUILLOTE   1 µW

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Re: Honda Express Build Thread

Post by GUILLOTE » Aug 12 2014 9:31am

Hi from Argentina! Nice Noped.. Time ago i wanted to do the same with a Suzuki FA 50..
What brushed motor would you recomend me? I want to cruce at 50Kh (30Mph) with no much effort or temp.. I think gear ratios may be similar..
Its difficult to buy here a brushless motor..
Hope your answer.. its my first reply.. :D
Guillermo, from Tostado, Santa Fe , Argentina.

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Dauntless   100 GW

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Re: Honda Express Build Thread

Post by Dauntless » Aug 12 2014 8:46pm

Yeah, I'd like to hear how it's holding up, too.
Any sufficiently advanced technology is INDISTINGUISHABLE FROM MAGIC!
- Arthur C. Clarke

quasse   100 µW

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Re: Honda Express Build Thread

Post by quasse » Aug 18 2014 1:19pm

Kent wrote:Can you give us a ballpark on finished weight and tire size?
I would guess weight is around 50-60lbs with batteries, it's definitely lighter than it used to be with an engine and a gas tank. Tire size is ~18.5 inches diameter, whatever that means in standard wheel sizes.
GUILLOTE wrote:What brushed motor would you recomend me? I want to cruce at 50Kh (30Mph) with no much effort or temp.. I think gear ratios may be similar..
Its difficult to buy here a brushless motor..
I'm afraid I have no experience with brushed motors or brushed controllers. I have only ever used brushless motors in large builds.
Dauntless wrote:Yeah, I'd like to hear how it's holding up, too.
I'm really happy with it so far. I wired up a voltage meter to fit in the gauge pod to reduce range anxiety, and wired the brake levers to an LED taillight I added on using a 48V-12V DC-DC converter. It's good for scooting around town when I don't want to jump on my bike.

devilishdesigner   10 µW

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Re: Honda Express Build Thread

Post by devilishdesigner » Feb 29 2016 4:08pm

Digging up an old thread here but I'd be keen to know why you didn't run the motor in where the crank used to be?

quasse   100 µW

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Re: Honda Express Build Thread

Post by quasse » Feb 29 2016 4:17pm

devilishdesigner wrote:Digging up an old thread here but I'd be keen to know why you didn't run the motor in where the crank used to be?
It was really tight in there and I would have had to remove quite a bit of metal to fit the hall sensor board in as well as the total length of the motor.

More importantly, it would have meant the crankshaft (which the clutch is mounted directly to) would have only been supported by one bearing instead of two. This would have put a front to back twisting moment load on that bearing from the force of the chain drive on the clutch, which the bearing isn't designed to support. With the longer shaft supported by two bearings, both bearings receive the correct radial load.

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